Two Resizing Features I’d Like to See

I have two features I’d like to see done in a Firefox extension. The goal
of each of them is to eliminate horizontal scrolling.

Shrink-Wrap

Provide a button, labelled “shrink-wrap”, that will resize the browser window
so it’s just big enough to display the page with no horizontal scrollbars.
Probably should have a reasonable minimum size (such as 640px) and maximum size
(the width of the screen).

Fit Width

This is the same feature, but in the other direction. Rather than resizing the
window to fit the content, resize the content to fit the window!

Probably works best when “Zoom Text Only” is unchecked.

I bet this sort of thing already exists in mobile phone browsers, but I want it
on my desktop.